Solar power is the collection and conversion of sunlight into electrical energy often using photovoltaic cells. Because there is no burning of fossil fuels during the capturing of sunlight, it is considered a “green” or renewable energy source. Because of concerns related to the strong relationship between burning fossil fuels and greenhouse gases, solar power technologies and installations have grown. The International Energy Agency has forecasted that by 2050, solar power could supply 27% of the world's electricity needs. Current methods of collecting solar power include the development of solar energy generating system (SEGS) or solar farms. Generally these systems require high capital costs, especially in the form of land and maintenance, prohibiting the growth and development of solar power as a primary energy source. Additionally, solar power is considered a less efficient energy source compared to coal and nuclear energy because it is an intermittent energy source as power cannot be generated at night.
Space-based solar power is the concept of harnessing solar power in space for use on Earth. Unlike current collection methods where the means for collecting solar energy reside on Earth, space-based solar power allows for the capturing of solar energy in space. By transitioning the point of collection to space, solar power can be captured more efficiently. The advantages of space-based solar power are twofold; a higher collection rate and a longer collection period. Because there is no atmosphere in lower Earth orbit to diffuse the energy transmitted by the sun, space-based solar power is more efficient than current solar power capturing methods. Additionally, the collection means in space-based solar power can constantly face the sun (i.e. no night) thereby overcoming the issue of intermittent generation.
Prior space-based solar power design concepts have relied on large, articulated structures that must be assembled in space requiring many launches of the component parts into orbit. These characteristics necessitate very large initial investments and technology developments to field an operational system. An example of such a system is the Naval Research Lab's 5 MW SSP design, which is comprised of two 18,300 square meter solar arrays and a one kilometer diameter microwave antenna. The SSP design merely generates 5 megawatts of energy and is estimated to be only 10% efficient. Further, it requires relay mirror to rotationally move in order to direct energy into the solar arrays thereby using some of the energy it captures. Lastly, the SSP design needs to be launched by multiple vehicles and assembled in orbit. For these reasons, the SSP design is considered cost prohibitive and inefficient.
Another example of prior designs is the Solar Power Satellite via Arbitrarily Large Phased Array (SPS-ALPHA). The SPS-ALPHA design is also a very large structure and requires thousands of mirrors to be rotated in order to redirect reflected sunlight onto a solar array. Like the SSP design, the SPS-ALPHA would require several launches in order to get all of the components to space where it would have to be assembled. Though the SPS-ALPHA overcomes several of the issues found in the SSP design, it is also considered to be cost prohibitive and inefficient.